// 需求：定义Person类，属性：名字和年龄，方法：吃饭
void main() {
  Person man = new Person();
  man.sayHello();
}

class Person {
  String name = '张三';
  int age = 28;
  String gender = '男';
  void sayHello() {
    print('我是$name,今年$age,性别$gender');
  }
}
